Blockages of arteries in human beings is unfortunately a widespread malady. As is well known, blockages or reduced blood flow through the coronary arteries to the heart can cause heart attacks, while blockages or reduced blood flow through the arteries to the brain can cause strokes. Similarly, arterial blockage or reduced blood flow through arteries to other parts of the body can result in grave consequences to the affected organ or limb.
The build up of atherosclerotic plaque is a chief cause of arterial blockages and reduced arterial blood flow. Not surprisingly, several methods have been introduced to alleviate the effects of plaque build up. One such method is the procedure known as angioplasty, which uses an inflatable device to compact and break up arterial stenoses. One typical angioplasty device is disclosed in U.S. Pat. No. 4,896,669 to Bhate, et al. The Bhate, et al. angioplasty device includes an inflatable balloon which is inserted while in its deflated state into an artery. The balloon is attached to one end of a hollow catheter, and the opposite end of the catheter is attached to a fluid source. Thus, the balloon can be inflated by infusing fluid from the fluid source into the balloon through the catheter.
To treat an arterial stenosis, the Bhate, et al. balloon is guided through the artery over a wire to position the balloon next to the stenosis, and the balloon is then inflated with fluid. As the balloon expands, the plaque which comprises the stenosis is compacted and broken up. The balloon is then deflated and removed from the artery.
While effective for breaking up stenoses, angioplasty devices such as the Bhate, et al. device discussed above do not remove the plaque from the artery. Consequently, the pieces of plaque can still disrupt blood flow or enter the blood stream. In either case they can cause future blockages in blood vessels. Fortunately, a procedure known as atherectomy has been devised which both clears the stenoses and then removes the pieces of the plaque which comprised the stenosis from the blood vessel. The technique of plaque removal by atherectomy typically includes inserting a guide wire into the affected artery and then advancing a hollow cutting device over the wire until the cutting device is positioned adjacent the stenosis (i.e., area of plaque build up) in the artery. Then, the cutting device is further advanced into the stenosis to cut a channel through the plaque, thereby increasing blood flow through the artery. Cut pieces of plaque can then be removed from the blood stream by drawing the pieces into the hollow cutting device.
Not surprisingly, a large number of atherectomy devices have been introduced. One such device is disclosed in U.S. Pat. No. 4,895,166 to Farr et al. which is assigned to the same assignee as the present invention. The Farr et al. device includes a frustum-shaped cutter which is attached to the distal end of a hollow catheter and is positioned into the artery over a guide wire. According to the Farr et al. disclosure, the cutter has two openings that define two straight cutting blades. As the cutter is advanced into the stenosis, the cutter is rotated to cut plaque. Excised plaque which enters the openings of the cutter is subsequently removed through the hollow catheter.
While the Farr et al. device is effective for its intended purpose, it happens that a helically-shaped uncut ridge of plaque can occasionally be left on the arterial wall as a rotating cutter advances through the stenosis. This ridge of plaque, along with fibers of plaque which extend from the ridge, can cause the clotting of blood adjacent the ridge and can perhaps lead to a restenosis of the affected artery. Accordingly, the present invention recognizes a need to provide an atherectomy device which cuts a channel through a stenosis, the channel having a smooth bore which is substantially free of plaque ridges and fibers.
It is therefore an object of the present invention to provide an atherectomy cutter that can cut a channel through a stenosis in an artery or a blood vessel of a living being. Another object of the present invention is to provide an atherectomy cutter which can be guided over a guide wire to the arterial stenosis to be removed. Yet another object of the present invention is to provide an atherectomy cutter that cuts a channel having a relatively smooth bore through an arterial stenosis. Finally, it is an object of the present invention to provide an atherectomy cutter which is relatively easy to use and cost-effective to manufacture.